diff options
Diffstat (limited to '')
| -rw-r--r-- | kernel/bpf/inode.c | 820 |
1 files changed, 820 insertions, 0 deletions
diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c new file mode 100644 index 000000000..4f841e167 --- /dev/null +++ b/kernel/bpf/inode.c @@ -0,0 +1,820 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Minimal file system backend for holding eBPF maps and programs, + * used by bpf(2) object pinning. + * + * Authors: + * + * Daniel Borkmann <daniel@iogearbox.net> + */ + +#include <linux/init.h> +#include <linux/magic.h> +#include <linux/major.h> +#include <linux/mount.h> +#include <linux/namei.h> +#include <linux/fs.h> +#include <linux/fs_context.h> +#include <linux/fs_parser.h> +#include <linux/kdev_t.h> +#include <linux/filter.h> +#include <linux/bpf.h> +#include <linux/bpf_trace.h> +#include "preload/bpf_preload.h" + +enum bpf_type { + BPF_TYPE_UNSPEC = 0, + BPF_TYPE_PROG, + BPF_TYPE_MAP, + BPF_TYPE_LINK, +}; + +static void *bpf_any_get(void *raw, enum bpf_type type) +{ + switch (type) { + case BPF_TYPE_PROG: + bpf_prog_inc(raw); + break; + case BPF_TYPE_MAP: + bpf_map_inc_with_uref(raw); + break; + case BPF_TYPE_LINK: + bpf_link_inc(raw); + break; + default: + WARN_ON_ONCE(1); + break; + } + + return raw; +} + +static void bpf_any_put(void *raw, enum bpf_type type) +{ + switch (type) { + case BPF_TYPE_PROG: + bpf_prog_put(raw); + break; + case BPF_TYPE_MAP: + bpf_map_put_with_uref(raw); + break; + case BPF_TYPE_LINK: + bpf_link_put(raw); + break; + default: + WARN_ON_ONCE(1); + break; + } +} + +static void *bpf_fd_probe_obj(u32 ufd, enum bpf_type *type) +{ + void *raw; + + raw = bpf_map_get_with_uref(ufd); + if (!IS_ERR(raw)) { + *type = BPF_TYPE_MAP; + return raw; + } + + raw = bpf_prog_get(ufd); + if (!IS_ERR(raw)) { + *type = BPF_TYPE_PROG; + return raw; + } + + raw = bpf_link_get_from_fd(ufd); + if (!IS_ERR(raw)) { + *type = BPF_TYPE_LINK; + return raw; + } + + return ERR_PTR(-EINVAL); +} + +static const struct inode_operations bpf_dir_iops; + +static const struct inode_operations bpf_prog_iops = { }; +static const struct inode_operations bpf_map_iops = { }; +static const struct inode_operations bpf_link_iops = { }; + +static struct inode *bpf_get_inode(struct super_block *sb, + const struct inode *dir, + umode_t mode) +{ + struct inode *inode; + + switch (mode & S_IFMT) { + case S_IFDIR: + case S_IFREG: + case S_IFLNK: + break; + default: + return ERR_PTR(-EINVAL); + } + + inode = new_inode(sb); + if (!inode) + return ERR_PTR(-ENOSPC); + + inode->i_ino = get_next_ino(); + inode->i_atime = current_time(inode); + inode->i_mtime = inode->i_atime; + inode->i_ctime = inode->i_atime; + + inode_init_owner(&init_user_ns, inode, dir, mode); + + return inode; +} + +static int bpf_inode_type(const struct inode *inode, enum bpf_type *type) +{ + *type = BPF_TYPE_UNSPEC; + if (inode->i_op == &bpf_prog_iops) + *type = BPF_TYPE_PROG; + else if (inode->i_op == &bpf_map_iops) + *type = BPF_TYPE_MAP; + else if (inode->i_op == &bpf_link_iops) + *type = BPF_TYPE_LINK; + else + return -EACCES; + + return 0; +} + +static void bpf_dentry_finalize(struct dentry *dentry, struct inode *inode, + struct inode *dir) +{ + d_instantiate(dentry, inode); + dget(dentry); + + dir->i_mtime = current_time(dir); + dir->i_ctime = dir->i_mtime; +} + +static int bpf_mkdir(struct user_namespace *mnt_userns, struct inode *dir, + struct dentry *dentry, umode_t mode) +{ + struct inode *inode; + + inode = bpf_get_inode(dir->i_sb, dir, mode | S_IFDIR); + if (IS_ERR(inode)) + return PTR_ERR(inode); + + inode->i_op = &bpf_dir_iops; + inode->i_fop = &simple_dir_operations; + + inc_nlink(inode); + inc_nlink(dir); + + bpf_dentry_finalize(dentry, inode, dir); + return 0; +} + +struct map_iter { + void *key; + bool done; +}; + +static struct map_iter *map_iter(struct seq_file *m) +{ + return m->private; +} + +static struct bpf_map *seq_file_to_map(struct seq_file *m) +{ + return file_inode(m->file)->i_private; +} + +static void map_iter_free(struct map_iter *iter) +{ + if (iter) { + kfree(iter->key); + kfree(iter); + } +} + +static struct map_iter *map_iter_alloc(struct bpf_map *map) +{ + struct map_iter *iter; + + iter = kzalloc(sizeof(*iter), GFP_KERNEL | __GFP_NOWARN); + if (!iter) + goto error; + + iter->key = kzalloc(map->key_size, GFP_KERNEL | __GFP_NOWARN); + if (!iter->key) + goto error; + + return iter; + +error: + map_iter_free(iter); + return NULL; +} + +static void *map_seq_next(struct seq_file *m, void *v, loff_t *pos) +{ + struct bpf_map *map = seq_file_to_map(m); + void *key = map_iter(m)->key; + void *prev_key; + + (*pos)++; + if (map_iter(m)->done) + return NULL; + + if (unlikely(v == SEQ_START_TOKEN)) + prev_key = NULL; + else + prev_key = key; + + rcu_read_lock(); + if (map->ops->map_get_next_key(map, prev_key, key)) { + map_iter(m)->done = true; + key = NULL; + } + rcu_read_unlock(); + return key; +} + +static void *map_seq_start(struct seq_file *m, loff_t *pos) +{ + if (map_iter(m)->done) + return NULL; + + return *pos ? map_iter(m)->key : SEQ_START_TOKEN; +} + +static void map_seq_stop(struct seq_file *m, void *v) +{ +} + +static int map_seq_show(struct seq_file *m, void *v) +{ + struct bpf_map *map = seq_file_to_map(m); + void *key = map_iter(m)->key; + + if (unlikely(v == SEQ_START_TOKEN)) { + seq_puts(m, "# WARNING!! The output is for debug purpose only\n"); + seq_puts(m, "# WARNING!! The output format will change\n"); + } else { + map->ops->map_seq_show_elem(map, key, m); + } + + return 0; +} + +static const struct seq_operations bpffs_map_seq_ops = { + .start = map_seq_start, + .next = map_seq_next, + .show = map_seq_show, + .stop = map_seq_stop, +}; + +static int bpffs_map_open(struct inode *inode, struct file *file) +{ + struct bpf_map *map = inode->i_private; + struct map_iter *iter; + struct seq_file *m; + int err; + + iter = map_iter_alloc(map); + if (!iter) + return -ENOMEM; + + err = seq_open(file, &bpffs_map_seq_ops); + if (err) { + map_iter_free(iter); + return err; + } + + m = file->private_data; + m->private = iter; + + return 0; +} + +static int bpffs_map_release(struct inode *inode, struct file *file) +{ + struct seq_file *m = file->private_data; + + map_iter_free(map_iter(m)); + + return seq_release(inode, file); +} + +/* bpffs_map_fops should only implement the basic + * read operation for a BPF map. The purpose is to + * provide a simple user intuitive way to do + * "cat bpffs/pathto/a-pinned-map". + * + * Other operations (e.g. write, lookup...) should be realized by + * the userspace tools (e.g. bpftool) through the + * BPF_OBJ_GET_INFO_BY_FD and the map's lookup/update + * interface. + */ +static const struct file_operations bpffs_map_fops = { + .open = bpffs_map_open, + .read = seq_read, + .release = bpffs_map_release, +}; + +static int bpffs_obj_open(struct inode *inode, struct file *file) +{ + return -EIO; +} + +static const struct file_operations bpffs_obj_fops = { + .open = bpffs_obj_open, +}; + +static int bpf_mkobj_ops(struct dentry *dentry, umode_t mode, void *raw, + const struct inode_operations *iops, + const struct file_operations *fops) +{ + struct inode *dir = dentry->d_parent->d_inode; + struct inode *inode = bpf_get_inode(dir->i_sb, dir, mode); + if (IS_ERR(inode)) + return PTR_ERR(inode); + + inode->i_op = iops; + inode->i_fop = fops; + inode->i_private = raw; + + bpf_dentry_finalize(dentry, inode, dir); + return 0; +} + +static int bpf_mkprog(struct dentry *dentry, umode_t mode, void *arg) +{ + return bpf_mkobj_ops(dentry, mode, arg, &bpf_prog_iops, + &bpffs_obj_fops); +} + +static int bpf_mkmap(struct dentry *dentry, umode_t mode, void *arg) +{ + struct bpf_map *map = arg; + + return bpf_mkobj_ops(dentry, mode, arg, &bpf_map_iops, + bpf_map_support_seq_show(map) ? + &bpffs_map_fops : &bpffs_obj_fops); +} + +static int bpf_mklink(struct dentry *dentry, umode_t mode, void *arg) +{ + struct bpf_link *link = arg; + + return bpf_mkobj_ops(dentry, mode, arg, &bpf_link_iops, + bpf_link_is_iter(link) ? + &bpf_iter_fops : &bpffs_obj_fops); +} + +static struct dentry * +bpf_lookup(struct inode *dir, struct dentry *dentry, unsigned flags) +{ + /* Dots in names (e.g. "/sys/fs/bpf/foo.bar") are reserved for future + * extensions. That allows popoulate_bpffs() create special files. + */ + if ((dir->i_mode & S_IALLUGO) && + strchr(dentry->d_name.name, '.')) + return ERR_PTR(-EPERM); + + return simple_lookup(dir, dentry, flags); +} + +static int bpf_symlink(struct user_namespace *mnt_userns, struct inode *dir, + struct dentry *dentry, const char *target) +{ + char *link = kstrdup(target, GFP_USER | __GFP_NOWARN); + struct inode *inode; + + if (!link) + return -ENOMEM; + + inode = bpf_get_inode(dir->i_sb, dir, S_IRWXUGO | S_IFLNK); + if (IS_ERR(inode)) { + kfree(link); + return PTR_ERR(inode); + } + + inode->i_op = &simple_symlink_inode_operations; + inode->i_link = link; + + bpf_dentry_finalize(dentry, inode, dir); + return 0; +} + +static const struct inode_operations bpf_dir_iops = { + .lookup = bpf_lookup, + .mkdir = bpf_mkdir, + .symlink = bpf_symlink, + .rmdir = simple_rmdir, + .rename = simple_rename, + .link = simple_link, + .unlink = simple_unlink, +}; + +/* pin iterator link into bpffs */ +static int bpf_iter_link_pin_kernel(struct dentry *parent, + const char *name, struct bpf_link *link) +{ + umode_t mode = S_IFREG | S_IRUSR; + struct dentry *dentry; + int ret; + + inode_lock(parent->d_inode); + dentry = lookup_one_len(name, parent, strlen(name)); + if (IS_ERR(dentry)) { + inode_unlock(parent->d_inode); + return PTR_ERR(dentry); + } + ret = bpf_mkobj_ops(dentry, mode, link, &bpf_link_iops, + &bpf_iter_fops); + dput(dentry); + inode_unlock(parent->d_inode); + return ret; +} + +static int bpf_obj_do_pin(const char __user *pathname, void *raw, + enum bpf_type type) +{ + struct dentry *dentry; + struct inode *dir; + struct path path; + umode_t mode; + int ret; + + dentry = user_path_create(AT_FDCWD, pathname, &path, 0); + if (IS_ERR(dentry)) + return PTR_ERR(dentry); + + mode = S_IFREG | ((S_IRUSR | S_IWUSR) & ~current_umask()); + + ret = security_path_mknod(&path, dentry, mode, 0); + if (ret) + goto out; + + dir = d_inode(path.dentry); + if (dir->i_op != &bpf_dir_iops) { + ret = -EPERM; + goto out; + } + + switch (type) { + case BPF_TYPE_PROG: + ret = vfs_mkobj(dentry, mode, bpf_mkprog, raw); + break; + case BPF_TYPE_MAP: + ret = vfs_mkobj(dentry, mode, bpf_mkmap, raw); + break; + case BPF_TYPE_LINK: + ret = vfs_mkobj(dentry, mode, bpf_mklink, raw); + break; + default: + ret = -EPERM; + } +out: + done_path_create(&path, dentry); + return ret; +} + +int bpf_obj_pin_user(u32 ufd, const char __user *pathname) +{ + enum bpf_type type; + void *raw; + int ret; + + raw = bpf_fd_probe_obj(ufd, &type); + if (IS_ERR(raw)) + return PTR_ERR(raw); + + ret = bpf_obj_do_pin(pathname, raw, type); + if (ret != 0) + bpf_any_put(raw, type); + + return ret; +} + +static void *bpf_obj_do_get(const char __user *pathname, + enum bpf_type *type, int flags) +{ + struct inode *inode; + struct path path; + void *raw; + int ret; + + ret = user_path_at(AT_FDCWD, pathname, LOOKUP_FOLLOW, &path); + if (ret) + return ERR_PTR(ret); + + inode = d_backing_inode(path.dentry); + ret = path_permission(&path, ACC_MODE(flags)); + if (ret) + goto out; + + ret = bpf_inode_type(inode, type); + if (ret) + goto out; + + raw = bpf_any_get(inode->i_private, *type); + if (!IS_ERR(raw)) + touch_atime(&path); + + path_put(&path); + return raw; +out: + path_put(&path); + return ERR_PTR(ret); +} + +int bpf_obj_get_user(const char __user *pathname, int flags) +{ + enum bpf_type type = BPF_TYPE_UNSPEC; + int f_flags; + void *raw; + int ret; + + f_flags = bpf_get_file_flag(flags); + if (f_flags < 0) + return f_flags; + + raw = bpf_obj_do_get(pathname, &type, f_flags); + if (IS_ERR(raw)) + return PTR_ERR(raw); + + if (type == BPF_TYPE_PROG) + ret = bpf_prog_new_fd(raw); + else if (type == BPF_TYPE_MAP) + ret = bpf_map_new_fd(raw, f_flags); + else if (type == BPF_TYPE_LINK) + ret = (f_flags != O_RDWR) ? -EINVAL : bpf_link_new_fd(raw); + else + return -ENOENT; + + if (ret < 0) + bpf_any_put(raw, type); + return ret; +} + +static struct bpf_prog *__get_prog_inode(struct inode *inode, enum bpf_prog_type type) +{ + struct bpf_prog *prog; + int ret = inode_permission(&init_user_ns, inode, MAY_READ); + if (ret) + return ERR_PTR(ret); + + if (inode->i_op == &bpf_map_iops) + return ERR_PTR(-EINVAL); + if (inode->i_op == &bpf_link_iops) + return ERR_PTR(-EINVAL); + if (inode->i_op != &bpf_prog_iops) + return ERR_PTR(-EACCES); + + prog = inode->i_private; + + ret = security_bpf_prog(prog); + if (ret < 0) + return ERR_PTR(ret); + + if (!bpf_prog_get_ok(prog, &type, false)) + return ERR_PTR(-EINVAL); + + bpf_prog_inc(prog); + return prog; +} + +struct bpf_prog *bpf_prog_get_type_path(const char *name, enum bpf_prog_type type) +{ + struct bpf_prog *prog; + struct path path; + int ret = kern_path(name, LOOKUP_FOLLOW, &path); + if (ret) + return ERR_PTR(ret); + prog = __get_prog_inode(d_backing_inode(path.dentry), type); + if (!IS_ERR(prog)) + touch_atime(&path); + path_put(&path); + return prog; +} +EXPORT_SYMBOL(bpf_prog_get_type_path); + +/* + * Display the mount options in /proc/mounts. + */ +static int bpf_show_options(struct seq_file *m, struct dentry *root) +{ + umode_t mode = d_inode(root)->i_mode & S_IALLUGO & ~S_ISVTX; + + if (mode != S_IRWXUGO) + seq_printf(m, ",mode=%o", mode); + return 0; +} + +static void bpf_free_inode(struct inode *inode) +{ + enum bpf_type type; + + if (S_ISLNK(inode->i_mode)) + kfree(inode->i_link); + if (!bpf_inode_type(inode, &type)) + bpf_any_put(inode->i_private, type); + free_inode_nonrcu(inode); +} + +static const struct super_operations bpf_super_ops = { + .statfs = simple_statfs, + .drop_inode = generic_delete_inode, + .show_options = bpf_show_options, + .free_inode = bpf_free_inode, +}; + +enum { + OPT_MODE, +}; + +static const struct fs_parameter_spec bpf_fs_parameters[] = { + fsparam_u32oct ("mode", OPT_MODE), + {} +}; + +struct bpf_mount_opts { + umode_t mode; +}; + +static int bpf_parse_param(struct fs_context *fc, struct fs_parameter *param) +{ + struct bpf_mount_opts *opts = fc->fs_private; + struct fs_parse_result result; + int opt; + + opt = fs_parse(fc, bpf_fs_parameters, param, &result); + if (opt < 0) { + /* We might like to report bad mount options here, but + * traditionally we've ignored all mount options, so we'd + * better continue to ignore non-existing options for bpf. + */ + if (opt == -ENOPARAM) { + opt = vfs_parse_fs_param_source(fc, param); + if (opt != -ENOPARAM) + return opt; + + return 0; + } + + if (opt < 0) + return opt; + } + + switch (opt) { + case OPT_MODE: + opts->mode = result.uint_32 & S_IALLUGO; + break; + } + + return 0; +} + +struct bpf_preload_ops *bpf_preload_ops; +EXPORT_SYMBOL_GPL(bpf_preload_ops); + +static bool bpf_preload_mod_get(void) +{ + /* If bpf_preload.ko wasn't loaded earlier then load it now. + * When bpf_preload is built into vmlinux the module's __init + * function will populate it. + */ + if (!bpf_preload_ops) { + request_module("bpf_preload"); + if (!bpf_preload_ops) + return false; + } + /* And grab the reference, so the module doesn't disappear while the + * kernel is interacting with the kernel module and its UMD. + */ + if (!try_module_get(bpf_preload_ops->owner)) { + pr_err("bpf_preload module get failed.\n"); + return false; + } + return true; +} + +static void bpf_preload_mod_put(void) +{ + if (bpf_preload_ops) + /* now user can "rmmod bpf_preload" if necessary */ + module_put(bpf_preload_ops->owner); +} + +static DEFINE_MUTEX(bpf_preload_lock); + +static int populate_bpffs(struct dentry *parent) +{ + struct bpf_preload_info objs[BPF_PRELOAD_LINKS] = {}; + int err = 0, i; + + /* grab the mutex to make sure the kernel interactions with bpf_preload + * are serialized + */ + mutex_lock(&bpf_preload_lock); + + /* if bpf_preload.ko wasn't built into vmlinux then load it */ + if (!bpf_preload_mod_get()) + goto out; + + err = bpf_preload_ops->preload(objs); + if (err) + goto out_put; + for (i = 0; i < BPF_PRELOAD_LINKS; i++) { + bpf_link_inc(objs[i].link); + err = bpf_iter_link_pin_kernel(parent, + objs[i].link_name, objs[i].link); + if (err) { + bpf_link_put(objs[i].link); + goto out_put; + } + } +out_put: + bpf_preload_mod_put(); +out: + mutex_unlock(&bpf_preload_lock); + return err; +} + +static int bpf_fill_super(struct super_block *sb, struct fs_context *fc) +{ + static const struct tree_descr bpf_rfiles[] = { { "" } }; + struct bpf_mount_opts *opts = fc->fs_private; + struct inode *inode; + int ret; + + ret = simple_fill_super(sb, BPF_FS_MAGIC, bpf_rfiles); + if (ret) + return ret; + + sb->s_op = &bpf_super_ops; + + inode = sb->s_root->d_inode; + inode->i_op = &bpf_dir_iops; + inode->i_mode &= ~S_IALLUGO; + populate_bpffs(sb->s_root); + inode->i_mode |= S_ISVTX | opts->mode; + return 0; +} + +static int bpf_get_tree(struct fs_context *fc) +{ + return get_tree_nodev(fc, bpf_fill_super); +} + +static void bpf_free_fc(struct fs_context *fc) +{ + kfree(fc->fs_private); +} + +static const struct fs_context_operations bpf_context_ops = { + .free = bpf_free_fc, + .parse_param = bpf_parse_param, + .get_tree = bpf_get_tree, +}; + +/* + * Set up the filesystem mount context. + */ +static int bpf_init_fs_context(struct fs_context *fc) +{ + struct bpf_mount_opts *opts; + + opts = kzalloc(sizeof(struct bpf_mount_opts), GFP_KERNEL); + if (!opts) + return -ENOMEM; + + opts->mode = S_IRWXUGO; + + fc->fs_private = opts; + fc->ops = &bpf_context_ops; + return 0; +} + +static struct file_system_type bpf_fs_type = { + .owner = THIS_MODULE, + .name = "bpf", + .init_fs_context = bpf_init_fs_context, + .parameters = bpf_fs_parameters, + .kill_sb = kill_litter_super, +}; + +static int __init bpf_init(void) +{ + int ret; + + ret = sysfs_create_mount_point(fs_kobj, "bpf"); + if (ret) + return ret; + + ret = register_filesystem(&bpf_fs_type); + if (ret) + sysfs_remove_mount_point(fs_kobj, "bpf"); + + return ret; +} +fs_initcall(bpf_init); |